Do You Really Want to Eat That Tuna?

Healthy eaters face a diner’s dilemma: Fish abound with beneficial omega-3 fatty acids. But they also contain potentially dangerous toxins. The Environmental Working Group, a public interest research organization in Washington, D.C., has sorted through the data and sees greater risks than those identified by the Food and Drug Administration.

The biggest concern is exposure to mercury, which especially accumulates at the top of the food chain. The FDA says children and pregnant women should avoid swordfish, shark, king mackerel, and tilefish; the agency has recently drafted a warning flagging tuna. Jane Houlihan of the Environmental Working Group argues that the warnings don’t go far enough. “If a woman ate canned tuna using current guidelines, she’d still almost certainly exceed the level of mercury that could put a baby in the womb at potential risk for brain damage,” she says. “And there is no known safe dose of mercury for anybody.” Separate studies, meanwhile, indicate farm-raised salmon may contain levels of PCBs that are linked to cancer. The FDA disputes the finding, but Houlihan urges the public to avoid farmed salmon until better data are available.

She recommends eating fish tested by the FDA as having low mercury levels. Haddock and flounder from unpolluted regions of the Atlantic coast are generally safe, as are wild Alaska salmon. Vegetable-fed farmed catfish and trout are also good bets. Scientists may someday expand healthy choices by engineering omega-3 acids into chicken or beef. But so far they’ve gotten only as far as an omega-3-rich mouse.